Two growing burger chains, Shake Shack and BurgerFi, stand out from the herd when it comes to serving beef raised without the routine use of antibiotics in the burger industry. They were the only restaurants to earn an “A” on the fourth annual Chain Reaction scorecard released today by six major consumer and environmental organizations. The vast majority of hamburger chains — 22 of the top 25, including giants such as McDonald’s — got an “F” grade because they lack established policies restricting antibiotic use in their beef supply chains.

We write you as physicians, infectious disease experts, and health professionals working to address the misuse of antibiotics in food animal production. We’re writing to express our concern with expanding conditional approvals in the Animal Drug User Fee Act reauthorization.

The third annual Chain Reaction report, which grades companies on their antibiotics policies and practices, found that 14 out of the top 25 restaurants in the U.S. have taken steps to restrict the routine use of antibiotics in the production of the chicken they serve, up from nine just one year ago. While restaurant chains made great progress on chicken, the groups who authored the report found that there were no new commitments to limit antibiotic use in beef and pork.

In response to the health risks posed by antibiotic-resistant bacteria, McDonald’s has announced it is implementing new targets for cutting antibiotic use in the global chicken supply, and plans to expand its commitment to fewer antibiotics in pork and beef.

With antibiotics, we can all enjoy the summer free from the worry that a stumble on the sidewalk or a minor burn from the grill could turn into a serious illness. So what could be a better centerpiece to the picnic table than meat raised without routine antibiotics?